On 2/13/18 5:42 AM, Ido Schimmel wrote: > On Tue, Feb 13, 2018 at 01:03:14PM +0200, Or Gerlitz wrote: >> On Tue, Feb 13, 2018 at 2:05 AM, David Ahern <dsah...@gmail.com> wrote: >>> Hardware supports multipath selection using the standard L4 5-tuple >>> instead of just L3 and the flow label. In addition, some network >>> operators prefer IPv6 path selection to use the 5-tuple. >> >> The HW supports using flow label and AFAIK that is the preferred approach >> by the community (?) >> >>> To that end, add support to IPv6 for multipath hash policy >> >> so a question comes up if/what are the disadvantaged >> to support 5-tuple. E.g Tom was commenting that such DPI is problematic >> when multiple IPv6 header extensions are used.
Pros and cons to both approaches (L3 only or L4). We (Cumulus Networks) use L4 5-tuple hash for both IPv4 and IPv6. When I asked around various experts all of them gave me a puzzled look as to why I was asking the question. Basically, the unanimous response was of course it is an L4 hash. > > Tom is much more qualified to answer this, but I think the problem is > that the flow label isn't always set. Also, apparently some devices > change the flow label mid flow. See: > > "At Fastly, this hashing is performed by an Ethernet switch ASIC, and to > avoid breakage, the IPv6 hashing function must not include the flow > label. As in IPv4, the hash function includes the source and destination > information in the L3 and L4 headers." > https://blog.apnic.net/2018/01/11/ipv6-flow-label-misuse-hashing/ > https://www.youtube.com/watch?v=b0CRjOpnT7w > https://pc.nanog.org/static/published/meetings/NANOG71/1531/20171003_Jaeggli_Lightning_Talk_Ipv6_v1.pdf >